An antenna (plural antennae or antennas), or aerial, is an electrical device which converts electric power into electromagnetic energy such as radio waves, and vice versa. It is usually used with a radio transmitter and/or a radio receiver to communicate information between points not connected by an electrical conductor. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals that is applied to an amplifier of a receiver.
Typically an antenna consists of an arrangement of metallic conductors (elements), electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of electrons forced through the antenna by a transmitter will create an oscillating magnetic field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements. These time-varying fields radiate away from the antenna into space as a moving transverse electromagnetic field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna elements, causing them to move back and forth, creating oscillating currents in the antenna.
Antennas can be designed to transmit and receive radio waves in all horizontal directions equally (omnidirectional antennas), or preferentially in a particular direction (directional or high gain antennas). In the latter case, an antenna may also include additional elements or surfaces with no electrical connection to the transmitter or receiver, such as parasitic elements, parabolic reflectors or horns, which serve to direct the radio waves into a beam or other desired radiation pattern. FIG. 2A shows a set of directional antenna designs utilizing one or more RF reflectors in order to concentrate RF radiation arriving from a specific direction onto an opening of an RF receiver.
Antennas are essential components of all wireless communication equipment, receivers and transmitters, used as part of systems for radio broadcasting, broadcast television, two-way radio, communications receivers, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, Bluetooth-enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise.
Wi-Fi is a wireless local area network that enables portable computing devices to connect easily to the Internet. Standardized as IEEE 802.11 a,b,g,n, Wi-Fi approaches speeds of some types of wired Ethernet. Wi-Fi has become the de facto standard for access in private homes, within offices, and at public hotspots.
Cellular data service offers coverage within a range of 10-15 miles from the nearest cell site. Speeds have increased as technologies have evolved, from earlier technologies such as GSM, CDMA and GPRS, to 3G networks such as W-CDMA, EDGE, CDMA2000, UMTS, HSDPA, LTE, etc. Mobile Satellite Communications may be used where other wireless connections are unavailable, such as in largely rural areas or remote locations. FIG. 1A shows two ground stations communicating though a satellite relay. FIG. 1B shows a satellite acting as a signal relay between multiple terrestrial ground-stations geographically dispersed across the United States.
Satellite communications are especially important for transportation, aviation, maritime and military use. A very small aperture terminal (VSAT) is a two-way satellite ground station or a stabilized maritime VSAT antenna with an antenna that is smaller than 3 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Data rates range from 4 kbit/s up to 4 Mbit/s and higher. New modulation technologies are pushing the limits of uplink and downlink speeds. VSATs usually access satellites in geosynchronous orbits. VSATs can be used to transmit narrowband data (e.g., point-of-sale transactions using credit cards, polling or RFID data, or SCADA), or broadband data (for the provision of satellite Internet access to remote locations, VoIP or video). VSATs are also used for transportable, on-the-move or mobile maritime communications. The antenna designs from FIG. 2A may be used as VSATs.
FIG. 2B includes a set of antenna array designs, which antenna arrays may also provide either fixed or steerable directivity for both reception and transmission of RF. As evident from the designs, antenna arrays can be quite large, depending upon the number and relative placement of the antenna array elements. Typically, the larger the placement between antennas or antenna elements of an array the better directivity is achievable. There is, however, a need in the field of wireless communication for improved directivity with smaller form factors.
As demand for wireless communication systems having higher data rates at lower power consumption levels and using smaller form factors increases, there is likewise an increased need in the field of wireless communication for improved antennas and antenna assemblies with capacity to provide high TX and RX directivity.